HIGH VOLTAGE ENGINEERING [ ] ACTIVE LEARNING ASSIGNMENT : TOPIC : CONDUCTION AND BREAKDOWN IN COMMERCIAL LIQUIDS. UNIVERSITY : GUJARAT TECHNOLOGICAL UNIVERSITY. COLLEGE : VADODARA INSTITUTE OF ENGINEERING. DEPARTMENT : ELECTRICAL ENGINEERING [E.E.– I]. SEMESTER : VI. PREPERED BY : [ MEET K. JANI ] [ BHARGAV M. JAYSWAL ] [ JESTY JOSE ] [ JOBIN ABRAHAM ] GUIDED BY : ASSO. PROF. ANJALIBA D. RANA. [ELECTRICAL DEPARTMENT] [ELECTRICAL DEPARTMENT] ACTIVE LEARNING ASSIGNMENT 1

 Contents:  Introduction  Suspended Particle Mechanism  Cavitation and Bubble Mechanism  Thermal Breakdown  Stressed Oil Volume Theory  References ACTIVE LEARNING ASSIGNMENT 2

 Introduction:  Commercial insulating liquids are not chemically pure and have impurities like gas bubbles, suspended particles etc. These impurities reduce the breakdown strength.  When breakdown occurs in these liquids, additional gases and gas bubbles are evolved and solid decomposition products are formed.  In general the breakdown mechanisms are classified as follows:  Suspended Particle Mechanism  Cavitation and Bubble Mechanism  Thermal Mechanism  Stressed oil volume theory ACTIVE LEARNING ASSIGNMENT 3

 Suspended Particle Mechanism: ACTIVE LEARNING ASSIGNMENT 4

 Cavitation and Bubble Mechanism: ACTIVE LEARNING ASSIGNMENT 5

 Thermal Breakdown:  Based on the experimental observations of extremely large currents just before breakdown. The high current pulses originate from the tips of the microscopic projections on the cathode surface with  densities of the order of 1 A/cm3. This high density current pulses give rise to localized heating of the oil which may lead to the formation of vapor bubbles.  When a bubble is formed, breakdown follows, either because of its elongation to a critical size or when it completely bridges the gap between the electrodes. ACTIVE LEARNING ASSIGNMENT 6

 Stressed Oil Volume Theory:  Breakdown strength is determined by the “largest possible impurity” or “weak link” in commercial liquids where minute traces of impurities are present.  The breakdown voltage determined by,  Gas content in the oil  Viscosity of the oil  Impurities present in the oil ACTIVE LEARNING ASSIGNMENT 7

 Stressed Oil Volume Theory{cont.}: ACTIVE LEARNING ASSIGNMENT 8

 References: 1.M.S. Naidu, V. Kamaraju “HIGH-VOLTAGE ENGINEERING”, McGraw Hill Education (India) Private Limited, Fifth Edition, Second Reprint, 2014, ISBN : C.L. Wadhwa “HIGH VOLTAGE ENGINEERING”, NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS, THIRD EDITION, Reprint, 2015, ISBN : breakdown-in-pure-liquid-dielectrics.pdf breakdown-in-pure-liquid-dielectrics.pdfhttps://srirajkumar.files.wordpress.com/2012/07/conduction-and- breakdown-in-pure-liquid-dielectrics.pdf ACTIVE LEARNING ASSIGNMENT 9

10  ANY QUESTIONS?